Backup lights material: Aluminum or Delrin ~ which is better and are both DIR?

[divad]

???

The copper strip that completes the circuit.

 

[Goose75]

???

Evad, let me take a stab at the whole point of his thread. The aluminum light does not require a metal strip (copper) to complete the circuit. That makes the light simpler and less components can mean less things to fail. If the aluminum light is less prone to failure, shouldn't it be the DIR recommendation?

I haven't done a comparison myself but I think the strip is unlikely to fail during a dive. Perhaps you could damage it during removal and installation of batteries but that is a pre and post dive operation. Aluminum, however, does corrode in saltwater if the coating becomes scratched or removed. This will probably result in surface pitting but is unlikely to cause a light failure during a dive. Good maintenance of the equipment should prevent or reduce corrosion. Still, I would go for the polymer since it doesn't have the problem.

Although complexity can increase likelihood of failure, sometimes more complexity can increase the robustness. In this case, I don't know that it is significant enough to make a difference one way or the other.

 

[detroit diver]

as someone who currently uses delrin backup lights, what problem do the Al lights solve?

When Abyss went out of business, I bought that light for around $20.00.

As Dearman has said, the differences here are so minimal that they seem to be insignificant. Both lights work equally for the task that they are required to perform.

 

[Jason B]

as someone who currently uses delrin backup lights, what problem do the Al lights solve?

So let's reverse the question. What problems do the delrin lights solve over Al? Side note...I use delrin, just curious as to your answer.

 

[divad]

When Abyss went out of business, I bought that light for around $20.00.

As Dearman has said, the differences here are so minimal that they seem to be insignificant. Both lights work equally for the task that they are required to perform.

Hey, I paid $30. I've never seen the inside of a delrin light but I have had the copper strip fall out of a plastic one. The difference in the end result is insignificant, but I just intuitively prefer the more direct "means" of the aluminum light.

 

[jonnythan]

Hey, I paid $30. I've never seen the inside of a delrin light but I have had the copper strip fall out of a plastic one. The difference in the end result is insignificant, but I just intuitively prefer the more direct "means" of the aluminum light.

Then use it.. no one will accuse you of doing it wrong for using an aluminum backup light.

 

[pete340]

Evad, let me take a stab at the whole point of his thread. The aluminum light does not require a metal strip (copper) to complete the circuit.

But is that actually true? The big problem with aluminum in electric circuits is that aluminum oxide doesn't conduct electricity, which is why it's no longer used in home wiring: too many fires. What happens when the aluminum contact point with the battery gets corroded? Seems like the light would stop working...

 

[divad]

What happens when the aluminum contact point with the battery gets corroded? Seems like the light would stop working...

There is no direct contact point. At the bottom, there is a spring which provides a couple of inches of contact with the housing. At the top, the battery is only in contact with the bulb asssembly which provide more than a couple of inches of contact with the housing. Why would the aluminum become corroded? Why would it become more corroded than copper? Why wouldn't I just clean off the corrosion?

 

[Dan Gibson]

Isn't it potentially possible for the aluminum container to cost more than an acetyl container? Aluminum takes a lot of energy to produce. The price could fluctuate a great deal more than acetyl. Maybe if the manufacturer of the lights didn't specify "Delrin" and purchased the material as acetyl, the price to produce it would be less.

Hey, I paid $30. I've never seen the inside of a delrin light but I have had the copper strip fall out of a plastic one. The difference in the end result is insignificant, but I just intuitively prefer the more direct "means" of the aluminum light.

 

[pete340]

There is no direct contact point. At the bottom, there is a spring which provides a couple of inches of contact with the housing.

Yup. That's one contact point.

At the top, the battery is only in contact with the bulb asssembly which provide more than a couple of inches of contact with the housing.

That's another.

Why would the aluminum become corroded? Why would it become more corroded than copper? Why wouldn't I just clean off the corrosion?

Any metal in contact with air or seawater gets corroded. Copper oxide conducts electricity, so minor corrosion doesn't matter. Aluminum oxide does not conduct electricity, so minor corrosion breaks the circuit. Sure, you can clean off the corrosion. You have to dig down to the bottom of the housing where it meets the spring if that's where it failed. Copper doesn't fail that way.

Edit, for clarity: Electrical components always corrode. The oxygen in the air is all that's needed. A slight amount of corrosion on the surface stops further corrosion. Copper components keep on working when they corrode, because the corrosion conducts electricity. Aluminum components stop working, because the corrosion does not conduct electricity. Twenty years or so ago in the US aluminum was allowed for house wiring because it was believed that suitably designed connectors could prevent corrosion. That belief turned out to be wrong, and they're no longer allowed. Too dangerous.